Alternating-current high-frequency generator.



E. P. W. ALEXANDERSON. ALTERNATING CURRENT HIGH FREQUENCY GENERATOR.APPLIOATION FILED FEB. 6, 1905.

905,621. Patented Dec. 1, 1908.

L1 v (1 5 i .Witnesses. Inventor: Em L F W. fl exanderson' W4 .f/zfl vUNITED STAT ES PATENT OFFICE.

ERNST F. W. ALEXANDERSON, OF SOHENECTADY, NEW YORK, ASSIGNOR TO GENERALELECTRIC COMPANY, A CORPORATION OF NEW YORK.

ALTERNATING-CURRENT HIGH-FREQUENCY GENERATOR.

Application filed February 6, 1905.

To all whom it may concern:

Be it known that I, ERNST F. W. ALEX- ANDERSON, a subject of the King ofSweden, residing at Schenectady, county of Schenectady, State ofNewYork, have invented certain new and useful Improvements inAlternetting-Current High-Frequency Generators, of which the followingis a specification.

My invention relates to dynamo-electric machines for producingalternating-current of high frequency, and its object is to produce acommercially operative machine capable of generating directly currentsof extremely high frequency, such as from 50,000 to 100,000 cycles persecond. In order to obtain such enormous frequency by magneticinduction, two things are obviously necessary; the distance betweenpoles must be extremely small, and the relative movement of the polesand armature conductors must be extremely high. My inventioncontemplates the use of a machine of the inductor type.

One feature of my invention consists in a novel arrangement of themoving part or inductor of the machine, which consists simply of twodisks tapered toward the periphery, so as to give the maximum factor ofsafety against centrifugal strains, and in so connecting the disks toeach other and to the supporting shaft that the strength of the disks isnot diminished for resisting bursting strains. Furthermore, thearrangement employed allows a certain flexibility which permits movingparts to adjust themselves with respect to their center of gravity whenhigh speed is attained.

In machines adapted for very high frequency, it is out of the questionto employ large laminated iron armature bodies, as in the ordinary lowfrequency machine, since the hysteresis and eddy current losses becomeenormous at high frequencies. consequently, been attempted. heretoforeto dispense with iron altogether, but the extremely small pole-pitch,which is necessarily employed in high frequency machines, results in adistribution of magnetic flux, when iron is omitted from the armature,which is substantially uniform throughout the field, so that little, ifany, electromotive force can be generated. By my invention I reduce theamount of iron. in that part of the armature body, which is traversed bythe field flux, to a minimum, while retaining suffi- Specification ofLetters Patent.

It has,

Patented Dec. 1, 1908.

Serial No. 244,298.

cient iron to prevent a substantially uniform distribution of the flux,as is obtained when iron is entirely omitted.

Another feature of my invention relates to a novel means which I employfor avoiding leakage fluxes, and thereby increasing the efficiency ofthe machine. Since the frequency factor of the armature reactance inhigh frequency machines is very high, it is essential that theinductance factor should be kept at its lowest possible value, in orderthat the reactance may not become excessive. The inductance factor isdirectly affected by the leakage fiux,that is the greater the amount offlux which leaks across the space, occupied by the armature conductor,between adjacent sections of armature laminations, the greater is theinductance of the conductor. Furthermore, this leakage flux produceseddy currents in the armature conductor, which result in forcing thearmature currents to the outer edges of the conductor, so that theapparent resistance of the conductor is increased. By reducing thisleakage flux, both the inductance and apparent resistance of thearmature are decreased, and the efliciency of the machine is therebyimproved.

One feature of my invention consists in providing novel means foraccomplishing the ends set forth above, consisting in providing a closedcircuit of high conductivity arranged to be threaded by the flux passingtransversely' across the space occupied by the armature conductors, orin other words, ar-

ranged in inductive relation to the leakage flux and acting as a screentherefor. More specifically stated this feature of my invention consistsin inserting a layer of conducting material between the armatureconductor and the iron laminations, which acts as a screen for theleakage flux.

Other features of my invention will ap ear from the followingspecification, and. wi l he more specifically pointed out in theappended claims.

My invention will best be understood by reference to the accompanyingdrawings, in which Figure 1 shows a sectional side elevation of theupper half of a high frequency generator constructed in accordance withmy invention; Fig. 2 shows an end elevation of a portion of the same, apart of one of the revolving disks being bro en away; and Fig. 3

shows an enlarged detail view of the active portion of the armature, andthe revolving magnetic poles.

In the drawings, the armature frame is shown as composed of two rings AA between which are clamped the armature laminations at. Theselaminations are arranged radially in the form of a ring, and threadedradially through this ring in a zigzag manner, as is clearly shown inFig. 2, is the armature conductor C. The inner ends of the laminations(t are clamped between two rings B B.

F represents the field coil which is preferably formed of a flat stripwound upon the inner supporting ring f, and clamped between the innerring and an outer ring f by means of the rivets The outer ring f isclamped between the rings B B, which also engage the inner ends of thearmature laminations.

The revolving portion of the magnet circuit of the machine consists ofan inductor comprising two steel disks D D, which are tapered, as shown,in order to afford the maximum of safety against centrifugal strength,and which carry on the inner sides of their peripheries the poles (Z d,respectively. The weight of these poles is balanced by rings or flangesd d" on the outer side of the peripheries of the disks. The strength ofsuch a disk as is shown in Fig. l is very greatly weakened by even asmall hole drilled through it, so that in the construction of themachine, all bolt-holes, and even a bore for the supporting shaft, arecarefully avoided. The two disks D D are secured to each other by meansof the tw flanges e and e, which are carried on the inner sides of theirrespective disks. The flange c is provided with an external screwthread,as shown, while the flange e is provided with an internal screw-thread.By means of this arrangement, the two disks may be forced into contactwith each other at their centers, so as to form with the arma turelaminations a a nearly closed magnetic circuit of comparatively highefficiency. The only portion of the magnetic circuit in which the fluxvaries, is the ring formed by the armature laminations, and the lengthof this portion of the circuit and consequently the eddy current andhysteresis losses are reduced to a minimum.

The disks are connected to the supporting shaft by a structure similarto that which binds them together. Each disk carries an external flangeg g, which is provided with external screw-threads adapted to be engagedby internal screw-threads on flanges at the peripheries of the caps H H.These caps or end-plates may be secured to opposite ends of the sectionsof the supporting shaft 71. h by screw-threads or any other suitableconnection. It will be seen that this construction avoids the use of allholes whatever within the bodies of the disks D D, and permits a certainamount of flexibility to be obtained, so as to allow the inductor torotate around its own center of gravity when running at high speed. Thisaction is aided by the small size of the shafts h h.

By referring to Fig. 3, it will be seen that with a pole-pitch small ascompared with the distance between opposite poles, a substantiallyuniform distribution of the flux would be produced in the space betweenopposite poles, if no iron were employed in the armature body; but onthe other hand, if iron or steel laminations are employed, as indicatedat a, and if the air-gap between the armature laminations and therevolving poles is made small, it is clear that a much greater flux willpass through the laininations which at any instant are directly oppositea pair of poles, than will pass through the set of laminations on eitherside midway between two pairs of poles. Consequently, the proportion oftotal flux, which is useful in generating an electromotive force in thearmature, is greatly increased by employing iron or steel laminat-ions.

In order to reduce to a minimum the leakage fluxes passing transverselythrough the space occupied by the armature conductor between adjacentsets of laminations, I cmploy the arrangement that is clearly shown inFig. 3. c 0 represent laminae of nonmagnetic, highly conducting,material, such as silver, which are placed between the armatureconductor C and the magnetic larninze a. These conducting laminae. arepreferably made of greater width than the magnetic lamina as isindicated at the rightdmnd of Fig. 3, and then are hammered over flushwith the outer edges of the laminze (1, so as to form a conductor ofappreciable cross-section at each outer edge of each turn of thearmature conductor O. The laminae 0 consequently form short-circuitedconductors of very low resistance, lying across the path of the leakageflux which tends to pass transversely from one set of magnetic laminarto the other, and act as efl'ective screens for the flux therebydecreasing the inductance and apparent resistance of the armature, andincreasing the efficiency of the machine.

It will be seen from Fig. 1 that the field coil F is practicallysurrounded by the rotary disks of the inductor. In order to make thenecessary connections to the field winding, I make use of theconstruction shown in Fig. 2. The end of the inside turn of the fieldcoil F is uninsulated from the inner su )porting rin f, and is pressedinto contact therewith both by the other turns of the field-spool, andalso by the clamping rivet f Those rivets, which are insulated from theturns of the field coil, form an electrical connection between innerring f and the outer ring f which is insulated from the outer turn ofthe fleldcoil This outer turn is led through an insulating bushing inthe outer ring f so as to form one terminal of the iield winding, asindicated at i. The other terminal i may be formed by a screw orbinding-post secured to the ring The leads 'from these terminals arebrought to the outer part of the machine by extending them through thelaminations a in place of two turns oi the continuous con ductor C,which turns are omitted from the armature winding. By this arrangement,the ring formed by the laminations a is unbroken, so that the reluctancebetween any two opposite poles d d on the revolving disks is equal,thereby avoiding any magnetic fluctuations and resulting eddy currentsin the disks themselves.

It is obvious that my invention comprises a number of features which,while I prefer to use them together, may, with advantage, be usedseparately, and which I desire to claim whether used together or not.Accordingly, I do not desire to limit myseh to the particularconstruction and arrangement of arts here shown, but aim in the appendedc aims to cover all modifications which are within the scope of myinvention.

What I claim as new, and desire to secure by Letters Patent of theUnited States, is,

1. In a dynamo-electric machine, two rotatably mounted disks of magneticmaterial tapering toward their centers, polar projections or teeth onthe inner sides of the peripheries of said disks, a flange on the outersides of the peripheries of said disks counterbalancing said polarprojections, a stationary coil adapted to magnetize said disks, and aconductor disposed between said polar projections.

2. In a dynamo-electric machine, two rotatably mounted disks of magneticmaterial magnetically united at their centers, polar projections on theinner sides of the peripheries of said disks, means for magnetizing saiddisks, a stationary ring of radially arranged lamina: of magneticmaterial disposed between said polar projections, and a continuousconductor threaded radially back and forth through said ring.

3. In a dynamo-electric machine, two rotatably mounted disks of magneticmaterial tapering toward their peripheries and bound together near theircenters, polar projections or teeth on the inner sides of theperipheries of said disks, a stationary ring of radially arrangedlaminee of magnetic material disposed between said polar projections, acon tinuous conductor threaded radially back and forth through saidring, and a stationary magnet coil concentric with said disks anddisposed between said disks and within said ring.

4. In a dynamo-electric machine, two rotatably mounted disks of magneticmaterial magnetically united at their centers, polar projections on theinner sides of the peripheries of said disks, a stationary ring ofradially arranged laminae of magnetic material disposed between said.polar projections, a continuous conductor threaded radially back andforth through said ring, a stationary magnet coil supported between saiddisks and within said ring, and terminal leads extending from saidmagnet outwardly through said ring.

5. In a dynamo-electric machine, a stationary frame, a ring of radiallyarranged magnetic laminae supported in said frame, a continuousconductor threaded radially back and forth through said ring, a magnetcoil supported. within said ring, two rotatably mounted disks ofmagnetic material on opposite sides of said coil magnetically united attheir centers, and polar projections or teeth on the inner sides of theperipheries of said disks extending into close proximity to said ring.

6. In a dynamo-electric machine, a stationary frame, a rin of radiallyarranged magnetic laminae supported. in said frame, a continuousconductor threaded radially back and forth through said ring, a magnetcoil supported within said ring, two rotatably mounted disks of magneticmaterial on opposite sides of said coil magnetically united at theircenters, polar projections or teeth on the inner sides of theperipheries of said disks extending into close proximity to said ring,and terminal leads from said field coil extending outwardly through saidring.

7. In a dynamo-electric machine, an inductor comprising two disks ofmagnetic material bound together at their centers and tapering towardtheir peripheries, and polar projections or teeth on the inner sides ofthe peripheries of" said disks, and flanges on the outer sides of theperipheries counter-balancing said polar projections.

8. In a dynamo-electric machine, an inductor comprising two paralleldisks of magnetic material tapering towards their peripheries andprovided at their peripheries with polar projections or teeth, one ofsaid disks being rovided near its center with an externally t readedflange and the other disk being provided with an internally threadedflange adapted to receive the flange on the first disk, whereby saiddisks are bound together near their centers.

9. In a dynamo-electric machine, an inductor comprising two paralleldisks of magnetic material tapering towards their peripheries andprovided at their peripheries with polar projections or teeth, saiddisks be ing provided near their centers with inwardly extending flangesand means for binding said flanges together.

10. In a dynamo-electric machine, an inductor comprising two paralleldisks of magnetic material tapering towards their peripheries andprovided at their peripheries with polar projections or teeth, saiddisks being provided near their centers with inwardly extending flanges,and means for binding said flanges together, and with outwardlyextending flanges and means for binding each flange to a rotatableshaft.

11. in a dynamo-electric machine, an in ductor comprising two paralleldisks of magnetic material tapering towards their peripheries andprovided at their peripheries with polar projections or teeth, saiddisks being provided near their centers with flanges on both inner andouter sides, the inner flanges being adapted to screw into each other tobind the disks together, and rotatably mounted members outside saiddisks adapted to screw into said outer flanges to support said disksrotatably.

12. In an alternating current generator for high frequencies, anarmature body comprising magnetic laminae, an armature conductorarranged between said laminae, and non-magnetic laminae of highconductivity inserted between said conductor and said magnetic laminae.

13. In an alternating current generator for high frequencies, anarmature body comprising magnetic laminae, an armature conductorarranged between said laminae, and non-magnetic laminae of highconductivity inserted on each side of the conductor, said non-magneticlaminae being of greater width than the magnetic laminae and havingtheir edges folded over the edges of said conductor.

14-. In a dynan'io-electric machine, two rotatably mounted disks ofmagnetic material magnetically joined at their centers and providea withpolar projections or teeth on the inner sides of their peripheries,means for magnetizing said disks, a ring of radially arranged magneticlaminae, disposed between said polar projections, a conductor threadedradially back and forth through said ring, and non-magnetic laminae ofhigh conductivity inserted between said conductor and said magneticlaminae.

15. In a dynamo-electric machine, an armature comprising a conductor,magnetic material on opposite sides of said conductor, and metal sheetsof high conductivity inserted between said conductor and said magneticmaterial and insulated from said conductor.

16. In a dynamoelectric machine, an armature comprising a conductor,magnetic material on opposite sides of the conductor, and a closedconducting circuit arranged to he threaded by the flux passingtransversely between the portions of magnetic material on opposite sidesof said conductor.

in witness whereof I have hereunto set my hand this lth day of February,1905.

ALEXANDERSON.

Witnesses:

BENJAMIN l3. HULL,

HELEN GRFORD.

